2.2. Extraction of Chitin from Crab Shell Waste

In the present work, chitin was extracted from crab shells by chemical method, as shown in Figure 1b, with some modifications [25]. Briefly, in the demineralization, 10 g of crab shells was treated with 300 mL of 1 M HCl aqueous solution at room temperature for 24 h. Then, deproteinization was carried out in 300 mL of 10% NaOH aqueous solution at 90 °C for 5 h. Next, 300 mL of ethanol solution was added, and the proteinized crab shells were bleached at 60 °C for 6 h. The solid part was filtered off and washed with distilled water to neutral pH. The extracted chitin was dried in the vacuum chamber for 24 h at room temperature. The yield of the purified chitin was calculated by Equation (1):

where m₀ and m are the weights of the crab shells and the extracted chitin (g), respectively.